This invention relates generally to a drive device for a web crosscutting apparatus in which a continuously moving sheet of material, such as corrugated cardboard, is to be cut; more specifically, the invention relates to such a device having an electrical drive motor, the number of revolutions of which is variable, and including a knife driven by the motor to cut the sheet; the moving speed of said knife is variable in order to cut a portion of the sheet.
Machines for cutting a continuously moving sheet of material require a drive device having a periodically variable number of revolutions in order to produce different length portions of the sheet. At the time of cutting, the circumferential speed of the knife is required to be equal to the speed at which the sheet of material passes in contact with the knife.
Such a drive device is disclosed in U.S. Pat. No. 3,680,616. In the patent, a knife running crosswise with respect to a moving web is raised by the action of two cam-type gearings. The movement of the knife is effected during cutting of the web in synchronization with the movement of the web; the drive velocity of the two cam-type gearings or transmissions is maintained constant. The result is that only one fixed length of the web may be cut in the device of the patent. In order to change the length of the web to be cut, the cam plates of the device must first be changed, and this requires undesirable rebuilding of the device.